1. Technical Field of the Invention
The present invention relates to a heat treatment apparatus, a calibration method for temperature measuring system of the heat treatment apparatus, and a heat treatment system.
2. Description of the Related Art
A vertical heat treatment apparatus, which performs a batch-type process on semiconductor wafers (which will be hereinafter referred to as xe2x80x9cwafer(s)xe2x80x9d), is known as one of the heat treatment apparatuses that performs a heat treatment on the wafers in a semiconductor device fabricating process. When performing the heat treatment, many wafers are carried by a wafer boat at intervals in the vertical direction and loaded into a reaction tube where the heat treatment, such as CVD process or oxidation process, is applied on the wafers.
Temperatures of the wafers have a great influence on the results of heat treatment. For instance, in case of film-deposition by the CVD process, a film-thickness changes depending on the temperatures of wafers. Accordingly, the temperatures of wafers during the heat treatment have to be controlled precisely. To this end, an accurate temperature measurement is necessary.
In a single-wafer heat treatment apparatus, the wafer is mounted face-to-face on a wafer table called a xe2x80x9csusceptorxe2x80x9d. Accordingly, the temperature of the susceptor becomes generally equal to a temperature of the wafer mounted thereon. Thus, it is possible to obtain the temperature of the wafer with high accuracy by measuring the temperature of the susceptor via the use of a thermoelectric couple embedded therein. However, in the vertical heat treatment apparatus, where a plurality of wafers are held by the wafer boat to be simultaneously processed, a temperature sensor must be arranged remote from the wafers.
Therefore, in the midst of changing the temperature in the reaction tube, there exists a difference between the temperature detected by the temperature sensor and the actual temperatures of the wafers.
In order to measure the temperatures of the wafers with high accuracy, the temperature measurement has to be performed after the temperature in the reaction tube has been stabilized. This means a reduction in throughput of the apparatus.
In order to solve such a problem, there have been temperature measuring methods recently developed, taking the transitional response into consideration. U.S. Pat. No. 5,517,594, for example, discloses such method.
In the method disclosed therein, the temperature measurement is executed by using ARX model. The constant matrixes in the ARX model are determined, upon actual experiments, based on detection signals from thermoelectric couples arranged in the reaction tube, detection signals from thermoelectric couples directly attached to test wafers and electric power supplied to heaters.
However, this method involves the following problems. First, the use of wafer with the thermoelectric couple might cause metals of the thermoelectric couple to be dispersed into the reaction tube, thereby causing it to be contaminated. Therefore, it is not preferable that the manufacturer of the heat treatment apparatus performs such experiments on the product apparatus to be supplied to the user. In this view, it is possible to perform an experiment for one of the apparatuses manufactured with the same specifications, and apply the model determined in said one of the apparatuses on the other apparatuses. However, even when manufactured with the same specifications, some variation will exist. Furthermore, after using the apparatus for a long term, a periodic change in the condition of the apparatus occurs.
Since the above method cannot cope with these problems sufficiently, there is a possibility of insufficient accuracy in determining the temperature.
Accordingly, the first object of the present invention is to improve the temperature measuring accuracy of the temperature measuring system of the heat treatment apparatus to be provided for the user.
The second object of the invention is to provide a method of calibrating the temperature measuring system of the heat treatment apparatus to be provided for the user.
In order to accomplish the above objectives, the present invention provides a heat treatment apparatus, which includes: a processing vessel defining a processing chamber for processing an object to be processed therein; a heater that heats the object; a thermal sensor arranged in the processing chamber; a temperature estimator that estimates a temperature of the object based on a detection signal from the thermal sensor; a temperature calibrator that corrects the temperature of the object estimated by the temperature estimator thereby to obtain a calibrated temperature of the object; and a controller that controls an operation of the heater based on the calibrated temperature of the object. The present invention also provides a heat treatment apparatus which includes: a processing vessel defining a processing chamber for processing an object to be processed therein; a heater that heats the object; a thermal sensor arranged in the processing chamber; a temperature estimator that estimates a temperature of the object at an estimation time-point based on a detection signal from the thermal sensor, the temperature estimator estimating the temperature of the object at the estimation time-point based on detection signals from the thermal sensor at several time-points preceding the estimation time-point; a temperature calibrator that corrects the temperature of the object estimated by the temperature estimator thereby to obtain a calibrated temperature of the object; and a controller that controls an operation of the heater based on the calibrated temperature of the object.
Furthermore, the present invention provides heat treatment apparatus which includes: a processing vessel defining a processing chamber for processing an object to be processed therein; a heater that heats the object; a thermal sensor arranged in the processing chamber; a temperature estimator that estimates a temperature of the object based on a detection signal from the thermal sensor; a temperature calibrator that corrects the temperature of the object estimated by the temperature estimator thereby to obtain a calibrated temperature of the object, the temperature calibrator having an offset table storing an offset value representing a difference between the temperature of the object estimated by the temperature estimator and a true temperature of the object, and an offset value adding part that adds or subtracts the offset value to or from the temperature estimated by the temperature estimator; a controller that controls an operation of the heater based on the calibrated temperature of the object; and an offset-value calculator that calculates the offset value to be stored in the offset table, based on the temperature of the object estimated by the temperature estimator and the true temperature of the object.
According to the second aspect of the present invention, there is provided a method of calibrating a temperature-detection system of a second heat treatment apparatus among a first and the second heat treatment apparatuses each having a processing vessel, a heater that heats an object to be processed, a thermal sensor and a temperature estimator that estimates a temperature of the object based on a detection signal from the thermal sensor, said method includes: (a) a temperature estimator adjusting process having the steps of: heating an object for temperature measurement placed in the processing vessel of the first heat treatment apparatus by the heater and measuring a true temperature of the object; and adjusting the temperature estimators of the first and second heat treatment apparatuses based on a result of the measurement of true temperature of the object; (b) a first heat-treatment/film-thickness measuring process including: a first heat-treatment step of heat-treating a first object for heat-treatment arranged in the processing vessel of the first heat treatment apparatus having the temperature estimator, having been adjusted in the process (a), under a designated heat-treatment condition; and a first film-thickness measuring step of measuring a film-thickness of a film formed on the first object; (c) a second heat-treatment/film-thickness measuring process including: a second heat-treatment step of heat-treating a second object for heat-treatment arranged in the processing vessel of the second heat treatment apparatus having the temperature estimator, having been adjusted in the process (a), under a designated heat-treatment condition; and a second film-thickness measuring step of measuring a film-thickness of a film formed on the second object; and (d) an offset-value calculating process having the steps of: comparing the film-thickness of the first object measured in the first film-thickness measuring step with the film-thickness of the second object measured in the second film-thickness measuring step, and calculating an offset value for calibrating the temperature of the object estimated by the temperature estimator of the second heat treatment apparatus based on the result of the comparison.
Furthermore, the present invention provides a heat treatment system, which includes: a heat treatment apparatus having a processing vessel defining a processing chamber for processing an object to be processed therein, a heater that heats the object and a thermal sensor arranged in the processing chamber; and a control device connected to the heat treatment apparatus, the control device having a temperature estimator that estimates a temperature of the object based on a detection signal of the thermal sensor, a temperature calibrator that corrects the temperature of the object estimated by the temperature estimator and a controller that controls an operation of the heater based on a calibrated temperature of the object corrected by the temperature calibrator.